Starting device for a twin cylinder internal combustion enginein a v-format

ABSTRACT

The invention relates to a starting device ( 2 ), for a twin cylinder internal combustion engine ( 1 ) with cylinders ( 4, 5 ) in a V-format, comprising an electrical starter motor ( 19 ) and a toothed gear drive ( 20 ), coupled thereto for transmission of the output torque from the starter motor ( 19 ) to a crankshaft ( 14 ) in the motor ( 1 ) and a sprag clutch ( 21 ) arranged between the drive ( 20 ) and the crankshaft ( 14 ), such that the starter motor ( 19 ) and the drive ( 20 ) are arranged in the V-shaped space ( 3 ) between the cylinders ( 4, 5 ) and above the crankshaft.

[0001] The present invention relates to a starter for a Vee twininternal combustion engine including an electric starter motor and agearing assembly coupled thereto as set forth in the preamble of claim1.

[0002] The Vee twin internal combustion engine in the present context isa two-cylinder engine in a Vee arrangement intended for use inmotorcycles. Saving weight in such an engine is of prime importance inthe present context since a lightweight engine enhances handling themotorcycle powered thereby. When such a motorcycle is put to use, forinstance, in cross-country sports events there is also the risk ofdamage when the engine is fitted with components exposed, for example,to impact by stones and grit thrown up by the front wheel of themotorcycle.

[0003] Hitherto, the motor of an electric starter on such a Vee twinengine was arranged either ahead of or behind the engine, as viewed inthe forward direction, where it is exposed either to stone and gritimpact or heat given off by the engine. Apart from this, thisarrangement results in the design lacking compactness, since a startermotor arranged ahead of the engine increases the room needed in theframe of the motorcycle for locating the Vee twin engine and a startermotor arranged behind the rear cylinder, as viewed in the forwarddirection, requires a relatively long distance for communicating thetorque from the starter motor to the crankshaft of the Vee twin engine.

[0004] The present invention is thus based on the objective ofeliminating the aforementioned disadvantages by providing a starter fora Vee twin internal combustion engine wherein the starter motor isarranged outside of the region exposed to stone and grit impact andwhich enables a more compact arrangement of the Vee twin engine of themotorcycle frame.

[0005] The invention devised for achieving this objective comprises thefeatures as set forth in claim 1. Advantageous aspects thereof read fromthe further claims.

[0006] In accordance with the invention a starter for a Vee twininternal combustion engine is now provided with an electric startermotor and a gearing assembly coupled thereto for communicating a torqueoutput by the starter motor to a crankshaft of the engine and anoverrunning clutch arranged between the gearing assembly and crankshaft,the starter motor and gearing assembly being arranged in the Vee-shapedinterspace between the cylinders above the crankshaft. This arrangementresults in the starter motor now being located outside of the regionexposed to stone and grit impact whilst significantly reducing the roomrequired for mounting the Vee twin engine in the frame of the motorcycleas compared to known arrangements.

[0007] In one advantageous further embodiment of the invention it isprovided for that the gearing assembly has arranged above the crankshaftan intermediate shaft for communicating the torque output by the startermotor to the crankshaft and the intermediate shaft additionally beingconfigured for balancing of masses and moments of first order. For thispurpose a gearwheel may be rotatably mounted on the intermediate shaft,by which the torque output is communicated to the crankshaft.

[0008] This configuration of the intermediate shaft achieves a functionconcentration so that, as compared to known Vee twin engines, areduction in weight is now achieved thanks to the starter in accordancewith the invention for the Vee twin engine equipped therewith. This isdue to the fact that the torque is now communicated from the startermotor to the crankshaft of the engine via a gearwheel mounted on theintermediate shaft and the intermediate shaft simultaneously serving asthe balancer shaft of the engine which thus now requires no separatebalancer shaft with the corresponding bearing locations as is the casewith known Vee twin engines. Now, in accordance with the invention thefunction of balancing of masses and moments of first order is integratedin the intermediate shaft of the starter.

[0009] For this purpose it is provided for that on the intermediateshaft for balancing of masses and moments of first order a crank armshaped or web-shaped balance mass is fixedly located both axially androtatively at one axial end portion each of the intermediate shaft sothat the web-shaped balance mass is located outside of or also betweenthe webs of the crankshaft of the Vee twin engine.

[0010] Further saving of space and thus enhancing the compactness of theVee twin engine equipped with the starter in accordance with theinvention is achievable by the intermediate shaft comprising at leastone sprocket for driving a timing chain for actuating the gas exchangevalve gear of the internal combustion engine. This means in other wordsthat the intermediate shaft may comprise two timing chain sprockets,each of which drives a timing chain for the camshaft drive of the frontand rear cylinder head of the internal combustion engine equipped withthe starter in accordance with the invention.

[0011] Equipping a liquid-cooled Vee twin engine with the starter inaccordance with the invention now makes it possible to provide animpeller fixedly located axially and rotatively at one axial end of theintermediate shaft for pumping a coolant of the internal combustionengine. Integrating the coolant pumping function of such a liquid-cooledinternal combustion engine in the intermediate shaft of the starter nowmakes it possible to eliminate two further bearing locations, namely thecoolant pump shaft bearings, as compared to known engine concepts. This,together with the integration of the function for balancing free massand moment forces in the intermediate shaft not only saves weight, italso reduces consumption, since as compared to known engine conceptsseveral bearing locations as a source of friction can now be eliminated.

[0012] In another further embodiment of the starter in accordance withthe invention it is provided for that for venting the crankcase of theinternal combustion engine the intermediate shaft comprises a holedrilled substantially through the full axial length thereof,transversely to which at one axial end of the intermediate shaft afull-length hole is drilled crosswise for centrifugal engine oilscavenging.

[0013] Now, any overpressure building up in the crankcase due to blow-byin the combustion chambers of the Vee twin engine and due to theoscillating movement of the pistons in the cylinder liners in thecrankcase can be relieved via the axial hole drilled lengthwise in theintermediate shaft, for example, into an air cleaner box communicatingwith a carburetion device of the Vee twin engine. Centrifugal engine oilscavenging through the intermediate shaft rotating, for example, at thespeed of the crankshaft and the hole drilled crosswise thereto preventsthe engine oil from gaining access to the air cleaner box.

[0014] It is also possible to implement engine oil scavenging by atleast one drilled passage provided in a web-shaped balance mass on theintermediate shaft. This drilled passage thus runs from the longitudinalhole through the intermediate shaft and through the balance mass,resulting in a major length of the drilled passage developing a highspeed at the end thereof due to rotation of the intermediate shaft forgood engine oil scavenging and thus diminishing the load on the engineair cleaner with engine oil.

[0015] In this arrangement, the starter motor is now able to communicateits torque output directly to the gearwheel mounted on the intermediateshaft or indirectly via interposed gear shafts. By suitably selectingthe transmission ratio between the starter motor and the crankshaft acomparatively low-power and thus small, compact electric starter motoris now sufficient for starting the Vee twin engine.

[0016] The overrunning clutch provided between the gearing assembly andcrankshaft opens the non-positive connection between the starter motorand the crankshaft as soon as a predefined difference in speed isattained, i.e. once the Vee twin engine has been started, when its speedis higher than that of the crankshaft prompted by the starter motorbefore the engine is started.

[0017] The invention will now be detailed with reference to the drawingin which:

[0018]FIG. 1 is a diagrammatic side view of a Vee twin engine showing astarter arranged in the Vee interspace between the two cylinders;

[0019]FIG. 2 is a partial sectional view through the starter as shown inFIG. 1;

[0020]FIG. 3 is a partial section view of the intermediate shaft of thestarter in accordance with a first embodiment;

[0021]FIG. 4 is a view of an intermediate shaft in accordance with afurther embodiment; and

[0022]FIG. 5 is a section taken through FIG. 4 in the direction of theline 5-5.

[0023] Referring now to FIG. 1 of the drawing there is illustrateddiagrammatically in a side view a Vee twin engine 1 including a starter2 arranged in the Vee-shaped interspace 3 between the front cylinder 4and rear cylinder 5.

[0024] As directly evident, the front cylinder 4 comprises an inlet 6and an outlet 7 whilst the rear cylinder 5 comprises an inlet 8 and anoutlet 9. In the embodiment as shown the Vee twin engine 1 comprises acylinder angle of approx. 75° located between the upright centerline 10of the front cylinder 4 and the upright centerline 11 of the rearcylinder 5.

[0025] Located in a crankcase 12 of the engine 1 behind or level withthe cap 13 is a crankshaft 14 of the Vee twin engine 1. Including in thecylinder head 15 of the front cylinder 4 and in the cylinder head 16 ofthe rear cylinder 5 is the valve gear in the form of inlet and outletvalves as well as the valve drive.

[0026] Illustrated in the plane of the drawing to the right of the cap13 and below the rear cylinder 5 is a multispeed gearbox 17 including achain sprocket 18 mounted on an output shaft of the gearbox by which thetorque output by the Vee twin engine 1 can be communicated via a drivechain (not shown) to the rear wheel of the motorcycle.

[0027] The starter 2 comprises an electric starter motor 19 and a gearassembly 20 coupled thereto (see FIG. 2) including a plurality of gearshafts and gearwheels for communicating the torque output by the startermotor 19 to the crankshaft 14 of the engine 1, an overrunning clutch 21being arranged between the crankshaft 14 and the gear assembly 20.

[0028] Referring now to FIG. 2 of the drawing the components of thestarter 2 will now be detailed.

[0029] The electric starter motor 19 is located on a casing boss 22 (seeFIG. 1) of the engine 1. Protruding from a housing of the electricstarter motor 19 is an output shaft 23 provided with spur teeth formating with the spur teeth of a gearwheel 24 on a gear shaft 25. In thisarrangement, the gearwheel 24 is non-rotatably located on the gear shaft25 by a Woodruff key 26 so that the torque output by the electricstarter motor 19 is introduced via the output shaft 23 and gearwheel 24into the gear shaft 25 on which a second gearwheel 27 is non-rotatablymounted axially offset from the gearwheel 24. It is just as possible tolocate the gearwheel 24 on the shaft 25 by means of a press fit insteadof the Woodruff key 26. In this arrangement the shaft 25 may berotatably mounted in the casing 22 by means of an antifriction bearing.

[0030] The gearwheel 27 mates with a gear shaft 28 provided with spurteeth, the gear shaft 28 being rotatably mounted via a bearing location29 in the casing 22. In this embodiment the teeth of the gear shaft 28are configured integral, although it is just as possible to locate,instead of the shaft 28, a journal in the casing 22 by means of areleasable bolting fastener. On the journal a rim gear may be axiallylocated rotatably mounted by a needle bearing and engaging the gearwheel27.

[0031] Via the gear shaft 28 or the aforementioned rim gear the torqueoutput by the electric starter motor 19 is directed into a gearwheel 31rotatably mounted by a needle bearing 32 on a intermediate shaft 30.

[0032] The gearwheel 31 mates with a gearwheel 34 rotatably mounted viaa friction bearing 33 or needle bearing on the crankshaft 14 so that thetorque output by the starter motor 19 ultimately rotates the gearwheel34. Arranged at the outer circumference of the hub 35 of the gearwheel34 is the overrunning clutch 21 so that with non-positive connection ofthe overrunning clutch 21 the torque output by the electric startermotor 19 is introduced via the gearwheel 34 and the outer cage of theoverrunning clutch 21 and bolt fastener 36 into a ring gear 37 which isconnected via a taper seat 38 and a parallel key (not shown) between thefrusto-conical end 39 of the crankshaft 14 and the ring gear 37positively to the crankshaft 14.

[0033] Thus, starting the Vee twin engine 1 on the motorcycle poweredthereby requires, for example, the starter button at the end of thehandlebar to be pressed by the rider to place the electric starter motor19 in circuit, prompting it to output a torque via the output shaft 23to the gearwheel 24. Via the further gearwheel 27, the spur gear shaft28, gearwheel 31 and gearwheel 34 as well as the overrunning clutch 21the torque output is communicated to the ring gear 37 and from there tothe crankshaft 14. As soon as the engine 1 has attained a crankshaftspeed in this way sufficient for starting and has commenced to run byitself, the speed of the crankshaft 14 significantly exceeds thestarting speed so that the overrunning clutch 21 opens to disengage thegear assembly 20 from the crankshaft 14.

[0034]FIG. 2 shows further a section detail of the intermediate shaft 30including a balance mass 39 arranged thereon. The intermediate shaft 30is shown in more detail in FIG. 3 of the drawing by way of a partialsection view.

[0035] The first balance mass 39 for balancing of free mass and momentforces of first order is non-rotatably located on the intermediate shaft30 by a Woodruff key 40. The gearwheel 31 rotatably mounted via bearing32 on the intermediate shaft 30 is omitted in FIG. 3 to simplify theillustration. Arranged in the region of the end of the intermediateshaft 30 located axially opposite the assembly of the first balance mass39 is a second balance mass 41, likewise non-rotatably located by meansof a Woodruff key 42. The Woodruff key 42 also ensures that the torqueis communicated between a spur gearwheel 43 and the intermediate shaft30. In this arrangement the gearwheel 43 mates with a gearwheel locatedon the crankshaft 14 and the transmission ratio in this gearwheelpairing may be 1 to 1.

[0036] The gearwheel 43 is located by a shaft nut 44 and a washer 45arranged between the gearwheel 43 and shaft nut 44 on the intermediateshaft 30.

[0037] Provided non-rotatably located on the intermediate shaft 30 aretwo timing chain sprockets 46, 47 by means of Woodruff keys, of whichonly one Woodruff key 48 is shown, so that via the sprockets 46, 47timing chains (not shown) can be driven extending up to the region ofthe cylinder heads 15, 16 of the cylinders 4, 5 of the engine 1 wherethey control breathing via the valve gear in the form of camshafts,valves and the like. In an alternative embodiment the timing chainsprocket 47 may also be configured integrally with the shaft 30.

[0038] Arranged non-rotatably axially fixed to the right-hand half ofthe shaft 30, as shown in the drawing, is an impeller 49 on theintermediate shaft 30 for circulating the coolant of a liquid-cooled Veetwin engine 1 through a heat exchanger.

[0039] For venting the crankcase 12 of the Vee twin engine 1 theintermediate shaft 30 comprises a longitudinal hole 50 drilledsubstantially full-length axially through the intermediate shaft 30 andat which the end of the intermediate shaft 30 located axially oppositethe impeller 49 fluidly communicates with a full-length transverse hole51. Due to the centrifugal effect of the rotating intermediate shaft 30,oil housed in the crankcase 12 of the engine 1, which is transportedthrough the longitudinal hole 50 due to the difference in pressurebetween that of the crankcase 12 and the environment or in the aircleaner box of the motorcycle by the gases to be expanded via thelongitudinal hole, is scavenged via the transverse hole 51, leaving onlythe gases to be expanded into the air cleaner via the outlet port 52 anda nozzle as may be provided thereat.

[0040] Via the intermediate shaft 30 the torque output by the electricstarter motor 19 is communicated on starting by means of the gearwheel31 mounted thereon to the crankshaft 14. In addition, the intermediateshaft 30 ensures balancing of free first order mass and moment forces bythe balance weights 39, 41 whilst serving via the timing chain sprockets46, 47 as the drive for the valve gear in the cylinder heads of theengine 1 in integrating also elements substantial to venting thecrankcase of the engine. As compared to known Vee twin engines thissolution thus totally eliminates a shaft solely for balancing the firstorder or primary forces. Arranging the impeller 49 on the intermediateshaft 30 also eliminates the need for a separate impeller shaft in thussaving bearing locations, which in turn results in a reduction in thefriction moment of the engine and thus also in a reduction inconsumption. Integrating the starter 2 in the Vee-shaped interspace 3 ofthe Vee twin engine achieves a remarkably compact engine design,resulting in a reduction in size of the surface area joining the engine1 to the frame of the motorcycle.

[0041] Referring now to FIG. 4 of the drawing there is illustrated amodified embodiment of an intermediate shaft 30. The intermediate shaft30 as shown in FIG. 4 of the drawing corresponds substantially to theintermediate shaft 30 as shown in FIG. 3 of the drawing, except fordifferences in venting the crankcase and in oil scavenging.

[0042] As directly evident the intermediate shaft 30 as shown in FIG. 4of the drawing comprises in the region of the balance mass 39 shown onthe left in the plane of the drawing a hole 53 for more location detailsof which reference is made to FIG. 5 of the drawing.

[0043] The hole 53 is the outlet port of a drilled passage 54 configuredin the balance mass 39 connecting the hole 53 to the center longitudinalhole of the intermediate shaft 30. In addition, to this drilled passage54 the balance mass 39 comprises a further drilled passage 55 having acorresponding outlet port 56 located to the rear of the plane as shownin FIG. 4 of the drawing.

[0044] The drilled passages 54, 55 serve to scavenge engine oil from thecrankcase breather, the reason for the larger radius on which the holes53, 56 lie as compared to the radius of the outlet ports of thetransverse hole 51 of the intermediate shaft 30 as shown in FIG. 3 ofthe drawing being an even more effective solution for engine oilscavenging for the same speed of the corresponding intermediate shaft30. Instead of being located on a shaft end provided with a male threadas shown in FIG. 3 of the drawing the impeller 49 may also be bolted tothe shaft end with a shaft-hub connection between the impeller 49 andshaft end in the form of a square profile, for instance. Evident fromFIG. 4 of the drawing are two further antifriction bearings 57, 58 inthe form of ball bearings by means of which the intermediate shaft canbe mounted in the crankcase of the Vee twin engine.

[0045] The starter 2 and more particularly the electric starter motor 19are protected from stone and grit impact as thrown up by the front wheelof the motorcycle which is particularly of importance in the case ofcross-country sports motorcycles.

[0046] It is to be noted that express reference is made to the claimsand to the drawing as regards any features of the invention not detailedabove.

What is claimed is:
 1. A starter (2) for an internal combustion engine(1) comprising twin cylinders (4, 5) in a Vee arrangement, including anelectric starter motor (19) and a gearing assembly (20) coupled theretofor communicating a torque output by said starter motor (19) to acrankshaft (14) of said engine (1) and an overrunning clutch (21)arranged between said gearing assembly (20) and said crankshaft (14),characterized in that said starter motor (19) and said gearing assembly(20) are arranged in the Vee-shaped interspace (3) between saidcylinders (4, 5) above said crankshaft (14).
 2. The starter as set forthin claim 1, characterized in that said gearing assembly (20) hasarranged above said crankshaft (14) an intermediate shaft (30) forcommunicating the torque output by said starter motor (19) to saidcrankshaft (14) by means of a gearwheel (31) rotatably mounted on saidintermediate shaft (30) and said intermediate shaft (30) also beingconfigured for dynamic balancing of first order masses and moments. 3.The starter as set forth in claim 2, characterized in that on saidintermediate shaft (30) for dynamic balancing a web-shaped balance mass(39, 41) is fixedly located both axially and rotatively at one axial endportion each of said intermediate shaft (30).
 4. The starter as setforth in claim 2 or 3, characterized in that said intermediate shaft(30) comprises at least one sprocket (46, 47) for driving a timing chainfor actuating the valve gear of said internal combustion engine (1). 5.The starter as set forth in any of the claims 2 to 4, characterized inthat an impeller (49) is fixedly located axially and rotatively at oneaxial end of said intermediate shaft (30) for pumping a coolant of saidinternal combustion engine (1).
 6. The starter as set forth in any ofthe claims 2 to 5, characterized in that for venting the crankcase (14)of said internal combustion engine (1) said intermediate shaft (30)comprises a longitudinal hole (50) drilled substantially through thefull axial length thereof, transversely to which at one axial end ofsaid intermediate shaft (30) a full-length hole (51) is drilledcrosswise for centrifugal oil scavenging of said internal combustionengine (1).
 7. The starter as set forth in any of the claims 2 to 5,characterized in that for venting the crankcase (14) of said internalcombustion engine (1) said intermediate shaft (30) comprises alongitudinal hole (50) drilled substantially through the full axiallength thereof, transversely to which at least one hole (54, 55) isdrilled crosswise in a web-shaped balance mass (39) for centrifugal oilscavenging of said internal combustion engine (1).
 8. The starter as setforth in any of the claims 1 to 7, characterized in that via a gearshaft (25) provided with two gearwheels (24, 27) arranged axially spacedaway from each other and a further gear shaft (28) provided with agearing said starter motor (19) is coupled to a gearwheel (31) rotatablymounted on said intermediate shaft (30) for communicating the torque. 9.The starter as set forth in claim 8, characterized in that thelongitudinal centerlines of said two gear shafts (25, 28) are offsetfrom the longitudinal centerline of said output shaft (23) of saidstarter motor (19) and the longitudinal centerline of said intermediateshaft (30) in the direction of said rear cylinder (5).
 10. The starteras set forth in any of the claims 1 to 9, characterized in that saidoverrunning clutch (21) opens the non-positive connection between saidstarter motor (19) and said crankshaft (14) as soon as a predefinedspeed difference is attained between the crankshaft and the intermediateshaft (30).
 11. A twin-cylinder internal combustion engine including astarter as set forth in any of the preceding claims.